A sheath valve is a type of one-way valve which permits a liquid, gas, or other flowable material to be dispensed, but does not permit anything to pass backwards through the valve, and so prevents possible contamination to the contents remaining in the dispensing container.
One form of one-way valve is a cylindrical core encompassed by an elastic cylindrical sheath, with the core having an entrance tube therein leading to a portion of the sheath, and an exit tube leading from the sheath. The two tubes are closed by the sheath and do not interconnect; but pressure applied to the liquid being dispensed serves to expand the sheath so that the liquid can pass from the entrance tube to the exit tube. Upon release of the pressure, the sheath contracts, sealing the valve against any possible reverse contamination.
Various patents have issued directed to this cylindrical valve. Examples of these include Gerber U.S. Pat. No. 4,846,810; Debush U.S. Pat. Nos. 5,279,330; 5,305,783; and 5,305,786; and Pardes U.S. Pat. No. 5,092,855. Each of these uses a cylindrical sheath surrounding a cylindrical valve core. This cylindrical structure is not only difficult and costly to manufacture, but also difficult and costly to assemble. A problem with a cylindrical sheath valve is that, to maintain tension, the inside diameter of the cylindrical sheath should be smaller in diameter than the outside diameter of the core, resulting in difficult assembly.
My co-pending application, Ser. No. 08/327,608, filed Oct. 24, 1994 is incorporated herein by reference. It is directed to a linear (not a cylindrical) sheath valve structure which provides an effective one-way valve. The present application is directed to a sheath valve which is vacuum actuated and is preferably, but not necessarily, a linear valve. It, too, is a one-way valve.